It has recently become appreciated by the general public that a fireplace opening into a building room and not provided with glass doors or the like closing the fireplace relative to the room into which the fireplace opens draws considerable room air into the fireplace for supporting combustion within the fireplace and thus reduces the air pressure within the building into which the fireplace opens. A reduction of air pressure within the building allows outside air to be drawn into the building through the numerous spaces and voids inherent in most building constructions with the result that many fireplaces actually cause a reduction of temperature within a building as opposed to increasing the temperature within the building. While the room into which an open fireplace opens may be warmed by a fire within the fireplace, during cold weather sufficient outside air is drawn into other areas of the building to actually effect a reduction of average internal temperature of the building. Accordingly, a need exists for means to supply the interior of a fireplace with combustion air from the exterior of the building in conjunction with a glass door assembly or the like which closes the fireplace relative to the room into which the fireplace opens.
Various forms of outside air vents for fireplaces including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 948,007, 2,819,711, 3,538,909, 4,108,144 and 4,136,666.